Tuesday, September 11, 2012

Red life forms on Mars - Halophiles?

Opportunity on Meridiani Planum Mars  NASA

BBC Science correspondent Rachel Buchanan wrote an article about a research project in pink life led by Dr Bonnie Baxter in which Dr Shil DasSharma has participated:
The Great Salt Lake in Utah has an otherworldly quality to it. It is a pink-tinged hyper-saline lake trimmed with a halo of salt that encrusts everything it touches.

This inland sea is home to dozens of species of salt-loving micro-organisms - so called halophiles - that thrive in the sodium-chloride-rich soup.

The lake and surrounding Bonneville Salt Flats are the remnants of a much larger, ancient body of water - Lake Bonneville - which drained away thousands of years ago.

But despite the lake's historic existence, little is known about its curious inhabitants, and that is something Dr Bonnie Baxter, of Salt Lake City's Westminster College, plans to change.

She has teamed up with leading halophile experts, including Dr Shil DasSarma of the University of Maryland, to take the first inventory of the lake's microbes.
Dr Baxter has similar aspirations for her Salt Lake inhabitants.

They employ solar-powered salt pumps to keep their internal salt concentrations lower than the water around them. But to drive those pumps, the microbes need to be at the surface which means basking in the Sun's damaging ultraviolet light all day.

But therein lies their powerful secret. The pink colour of the lake is due, in part, to the pigments - carotenoids - that the lake's microbes produce.

These shield their DNA from damage, like an in-built sunscreen, a characteristic Dr Baxter believes could be exploited.

Bonneville Salt Plains Utah

In Dr DasSarma, she has a partner of impeccable pedigree for the project. He was the first to sequence the genome of a halophile - Halobacterium species NRC-1 - in 2000.

Work on its Utah cousins has only just begun but Dr DasSarma says their initial results are showing just how novel these organisms are.

When you compare the DNA of a new species to a gene bank to see if their genes resemble those of known organisms, "normally, three out of four times you find something similar," Dr DasSarma said.

"But when you do this with the Salt Lake, the majority of genes are novel - they are like nothing on Earth."

It is appropriate then that parallels are being drawn between locations like this and Meridiani Planum on Mars. This is where Nasa's Opportunity rover has discovered it is parked on top of an evaporate basin like Utah's Bonneville flats, the remnants of an ancient Martian salty sea.

As the conditions on early Mars got colder and harsher, it lost liquid water through evaporation or sequestration into permafrost.

Remaining bodies of water would have been increasingly salty places, and then finally all liquid water disappeared, and the salt deposits eventually lithified into the evaporate rocks the rover sees today.

Any early Martian microbe would have had to withstand a high salt environment and intense UV radiation. Sound familiar?

Rachael Buchanan
Read the entire article in BBC NEWS Science/Nature May 18 2004

Monday, September 10, 2012

Shil DasSarma - first life pink?

Professor Shil DasSarma University of Maryland marinebiogech.org

Ker Than writes about a suggestion by microbial genetist Shiladitya DasSarma from University of Maryland Center of Marine Biotechnology, that early life on Earth may not have been green nor black but rather pink!
The earliest life on Earth might have been just as purple as it is green today, a scientist claims.

Ancient microbes might have used a molecule other than chlorophyll to harness the Sun's rays, one that gave the organisms a violet hue.

Chlorophyll, the main photosynthetic pigment of plants, absorbs mainly blue and red wavelengths from the Sun and reflects green ones, and it is this reflected light that gives plants their leafy color. This fact puzzles some biologists because the sun transmits most of its energy in the green part of the visible spectrum.

"Chlorophyll was forced to make use of the blue and red light, since all the green light was absorbed by the purple membrane-containing organisms," said William Sparks, an astronomer at the Space Telescope Science Institute (STScI) in Maryland, who helped DasSarma develop his idea.
LiveScience 2007

As a beginner student of the subject, IMHO discussion of the pigment colours on early life forms upon Earth is a good sample of using natural selection as the main tool for explaining the evolution of life.

The idea is there and is fitted to the theoretical discussion of how green might have become the dominant colour and chlorophyll take the leading position in plant life.

Let us suppose a fight for survival on early Earth - let us assume that we need sun to generate energy - who might be competing forcing the choice between black, pink, blue and green?

Indeed, a good show case of evolutionary biology at work explaining the greenness of the plant world!

Friday, September 7, 2012

Pea aphid photosynthesis!

Pea aphid (greenflie) sucking sap

This is a God and Molecular Biology bookmark
Will we ever... photosynthesise like plants
Ed Yong
BBC News Future Science and Environment September 8 2012
As a rule, animals cannot photosynthesise, but all rules have exceptions. The latest potential deviant is the pea aphid, a foe to farmers and a friend to geneticists.

Last month, Alain Robichon at the Sophia Agrobiotech Institute in France reported that the aphids use pigments called carotenoids to harvest the sun’s energy and make ATP, a molecule that acts as a store of chemical energy. (Nature 2010)

The aphids are among the very few animals that can make these pigments for themselves, using genes that they stole from fungi.

Green aphids (with lots of carotenoids) produced more ATP than white aphids (with almost none), and orange aphids (with intermediate levels) made more ATP in sunlight than in darkness.